The present invention relates to bonding apparatus, particularly to bonders for electronic components, and more particularly to a pressure activated diaphragm bonder for bonding chips to a substrate.
Since the initial development of integrated circuits, substantial efforts have been directed to the development of processes and apparatus for attaching components to a support substrate and interconnecting the various components. This has been accomplished by various techniques involving gluing, soldering, compression, anodic bonding, etc., each of these techniques being generally referred to as "bonding". These prior efforts are exemplified by U.S. Pat. No. 3,516,155 issued Jun. 23, 1970 to C. W. Smith; U.S. Pat. No. 3,699,640 issued Oct. 24, 1972 to B. H. Cranston et al; U.S. Pat. No. 4,184,623 issued Jan. 22, 1980 to B. Strasser; U.S. Pat. No. 4,607,779 issued Aug. 26, 1986 to C. D. Burns; U.S. Pat. No. 4,903,885 issued Feb. 27, 1990 to H. Schwarzbauer; U.S. Pat. No. 5,158,226 issued Oct. 27, 1992 to H. Schwarzbauer; U.S. Pat. No. 5,222,648 issued Jun. 29, 1993 to T. Takano; and U.S. Pat. No. 5,365,656 issued Nov. 22, 1994 to D. W. Dahringer et al.
With the development of high density, high performance integrated circuits, both the effectiveness of the attaching techniques and the related costs have lead to substantial efforts in packaging techniques. High density, high performance packaging of integrated circuit chips can be accomplished by attaching bare chips to a substrate and interconnecting them to form a multichip module or hybrid package. Attachment of chips to substrates on multichip modules and hybrid packages is generally accomplished with adhesives (epoxies, polyimides), hard solders (AuSi, AuSn) or flip-chip solder bumps (PbSn). Hard solders offer considerable thermal, mechanical, and electrical advantages over adhesives and flip-chip processes. Hard solders can be thick or thin film. Thick film solders are preformed into sheets which are placed between the chip (die) and the substrate, while thin films are deposited by evaporation or sputtering solder onto the backside of the chip or die, onto substrate, or onto both.
In both the thick and thin film solder approaches, the temperature is raised above the melting point of the solder, and held there until melting has occurred. The die or chip is held in position, and pressure is exerted on the chip during melting. High pressure generally results in better, void-free bonds, because the oxide layer on the solder is more readily fractured, allowing a flow of solder to occur.
Typical prior methods for holding the chips and applying pressure include a spring-loaded block arrangement and a robotic pick-and-place handler. The spring-loaded block arrangement is problematic from a chipping and uniformity point of view, while the robotic pick-and-place method does not allow sufficiently high pressure to be applied, and is difficult and expensive to configure in an inert atmosphere or vacuum environment.
The present invention overcomes the above-referenced problems by providing a chip-to-substrate bonder that utilizes thin film eutectic solders, a template to accurately position the chips on the substrate, and a pressure activated diaphragm for applying uniform high pressure to the chips during melting of the solder by a heating means, without causing chipping or cracking thereof. Thick film preforms would also work with this bonder. The bonder of this invention also enables simultaneous attachment of different size chips to the substrate.